One of the goals of the Healthy People 2000 initiative is to increase breastfeeding rates in the U.S. to 75% immediately following birth and to 50% at 5 to 6 months of age. Breastfeeding new born infants is widely thought to lead to health benefits in infants including reduced upper and lower respiratory tract infection, reduced gastrointestinal tract infection, reduced ear infection and lower rates of asthma and allergies among infants and children. Most research to date, however, has focused on the benefits of breastfeeding in non-industrialized countries, where it is not surprising that breastfeeding has demonstrable effects on health status given general poorer nutrition, health care and sanitation conditions frequently present in these areas. Research on breastfeeding in the U.S. has provided mixed evidence regarding the health benefits of breast feeding compared to formula feeding. In addition, the literature regarding breastfeeding outcomes in the U.S. has focused primarily on middle to upper middle class white populations. This research has also suffered from small sample sizes and has not adequately controlled for the selection bias and confounding factors inherent in the modeling of breast feeding outcomes. This study will use the Medicaid claims of a group approximately 950 infants linked to Vital Statistics and WIC files containing information about these infants, their families and their households. The specific aims of this study are: 1) To determine the impact of feeding method (breast v. bottle feeding) on health services utilization and costs among infants enrolled in Medicaid at 6, l2 and 24 months after birth; 2) To determine the factors which influence the choice to breastfeed or formula feed an infant in this low income population; and 3) To identify the factors which determine the duration for which mothers enrolled in Medicaid and WIC choose to breast feed their infants. Multivariate analytic methods will be used which will address the model specification complexities (primarily confounding and selection bias) inherent in data involving the health outcomes of breastfeeding.